The present invention relates in general terms to the field of motor vehicle headlights, and in particular those which are capable of emitting, from a single light source, two different light beams selectively, with selection of the type of light beam to be emitted being obtained by means of relative motion between a reflector of the headlight and the light source.
Headlights of the above general type are already known in the prior art. For example, French published patent specification No. 2 765 308 describes a headlight in which the reflector is displaced with respect to the light source between two positions, firstly by performing a translation (that is to say straight line motion) of the reflector in the general direction of the illumination given by the headlight, and secondly by controlling an adjusting device in such a way as to effect a slight raising of the light emitted, by tilting the component that supports the light source.
That type of headlight is not suitable for use in small vehicles or medium size vehicles, because of the large number of components involved, the size of the components, and the movements involved, because in such vehicles the amount of space available in the engine compartment tends to be more and more restricted.
An object of the present invention is to overcome the above mentioned drawback of the prior art.
According to the invention, a vehicle headlight having a cam for displacing a reflector and a light source with respect to each other, for producing two different light beams, the said cam comprising a first member and a second member and being adapted to convert rotational movement of the first cam member about an axis of rotation into a first translational movement of the second cam member, is characterised in that the said first translational movement is collinear with the axis of rotation.
Thus, the fact that the first straight line movement takes place in a manner such that it is collinear with the axis of rotation, enables the number, size and displacement of the components of the mechanism for effecting relative displacement between the reflector and the light source to be reduced as compared with the above mentioned headlights of the prior art.
The reduction in the number of components as compared with the prior art arrangements, which are capable of emitting from a single light source two different kinds of light beam, greatly assists industrial production of the headlights, by reducing the difficulties which are connected with the fact that a high number of components, with complex production lines, make it necessary to adopt production processes which are at the very limits of currently available capabilities. All this therefore means that a headlight in accordance with this invention is easier to manufacture industrially, and is also easier to standardise. In this connection, it is possible to make a lamp support or lamp holder, and a cam system, which are the same for all the headlights for all types of vehicles. This enables the cost of the main beam and dipped beam illumination functions to be reduced.
Preferably, the first cam member and the second cam member are adapted to perform a second translational movement with respect to each other in a plane at right angles to the axis of rotation. This feature enables more precise positioning of the reflector to be obtained with respect to the light source, mainly in the dipped beam position, and with a reduced number of components.
According to a preferred feature of the invention, one of the cam members, that is to say the first cam member and the second cam member, has a toothed sector so that it can be driven in rotation about the axis of rotation by a micromotor. Preferably then, the micromotor is supplied and controlled by the voltages which are available on the electrical networks of the vehicle for dipped beam lighting and main beam lighting. There is therefore no need to modify the wiring as already provided in the vehicle for conventional headlights.
Preferably, the first cam member is adapted to exert a thrust on the second cam member parallel to the axis of rotation, during its rotation with respect to the second cam member.
According to a further preferred feature of the invention, at least one of the said first cam member and second cam member includes a ramp having a surface extending away from a plane at right angles to the axis of rotation, in a path describing a circular arc about the said axis.
Preferably again, the said first cam member and second cam member are formed with a passage for a lamp or a lamp holder.
In preferred embodiments of the invention, when the headlight is fitted on a vehicle, the said first and second straight line motions (or translational movements) are effected along a horizontal axis and a vertical axis respectively.
Further features and advantages of the invention will appear on a reading of the following detailed description of some preferred embodiments of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings.